communication channels and types

Importance of channels in communication and

types of channels

ContentsIntroductionCommunication modelDesign factorsTypes of communication channelsGuided(wired) channelsUnguided(wireless) channelsConclusion

IntroductionCommunication channel is a connection between

transmitter and receiver through which Data can be transmitted.

Communication channel also called as communication media or transmission media

Communication model

Transmitter Communication channel Receiver

Design FactorsBandwidth

- Higher bandwidth gives higher data rateTransmission impairments

- eg. attenuationInterferenceNumber of receivers in guided media

- More receivers introduces more attenuation

Types of Communication channelCommunication

channel

Guided (wired) Unguided (wireless)

Twisted pair

Coaxial cable

Optical fiber

Satellite microwave

Terrestrial microwave

Broadcast radio

• Other types are Under Water Acoustic Channels, Storage Channels like magnetic tapes, magnetic disks etc.

Twisted-pair cable

One of the wires carries signal, the other is used only as a ground reference.

Number of twists per unit length determines the quality of the cable.

Types in twisted pair cables Shielded twisted-pair cable Unshielded twisted-pair cable Categories of Twisted-Pair Cables

Category 1- 0.1 Mbps Category 2- 2 Mbps Category 3- 10 Mbps Category 4- 20 Mbps Category 5- 100 Mbps Category 6- 200 Mbps Category 7- 600 Mbps

Coaxial cable

• Used for both analog and digital signals

• Effectively used at higher data rate and higher bandwidth

• For analog signals need amplifiers every few km

• For digital signals requires repeater every 1km

Optical fiber Refraction and reflection

Propagation modes

Terrestrial microwaveRequires fewer repeatersUse a parabolic dish to focus

a narrow beam.1-40GHz frequencies

Satellite communicationReceives on one frequency, and

transmits on another frequencyeg. uplink 5.925-6.425 GHz &

downlink 3.7-4.2 GHz• Height 35,784km• Spaced at least 3-4° apart

Broadcast RadioRadio frequency range is 3kHz to 300GHzUse broadcast radio of 30MHz - 1GHz, for:

FM radioUHF and VHF television

Is a unidirectionalSuffers from multipath interference

Reflections from land, water, other objectsAre used for multicasts communications, such as radio and

television, and paging system.

ConclusionCommunication channel is essential for communication

systems. The transmission characteristics are important in selecting channel because they directly affect the communication quality.

Different types of communication channels have different transmission characteristics and costs, they are used in different applications.

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